The present invention relates to a radiation image information reading apparatus, and more particularly to a radiation image information reading apparatus which includes means for determining whether reading conditions and/or image processing conditions are appropriate or not when radiation image information is read from a stimulable phosphor sheet, for example, and processed for image display or recording.
There have recently been developed radiation image recording and reproducing systems for producing the radiation image of an object using a stimulable phosphor material capable of emitting light upon exposure to stimulating rays (see, for example, Japanese Laid-Open Patent Publications Nos. 55-12429, 55-103472, 55-116340, 55-87970, etc). These radiation image recording and reproducing systems are finding wider use particularly in the medical field. When a certain phosphor is exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays, or ultraviolet rays, the phosphor stores a part of the energy of the radiation. When the phosphor exposed to the radiation is subsequently exposed to stimulating rays such as visible light, the phosphor emits light in proportion to the stored energy of the radiation. The phosphor exhibiting such a property is referred to as a "stimulable phosphor".
In the radiation image recording and reproducing system employing such a stimulable phosphor, the radiation image information of an object such as a human body is stored in a sheet having a layer of stimulable phosphor, and then the stimulable phosphor sheet is scanned with stimulating rays such as a laser beam, so that the stimulable phosphor sheet emits light representative of the radiation image. The emitted light is then photoeectrically detected to produce an image information signal that is electrically processed for generating image information which is recorded as a visible image on a recording medium such as a photographic photosensitive material or displayed as a visible image on a display unit such as a CRT or the like.
Some radiation image recording and reproducing systems are arranged to effect preliminary and main reading modes. In the preliminary reading mode, a stimulable phosphor sheet with a recorded radiation image is scanned with a light beam of a lower level so that the recorded radiation image is roughly read from the stimulable phosphor sheet, and the obtained image signal is analyzed to produce optimum reading conditions which are best suited to the intensity of the radiation that was applied to the stimulable phosphor sheet at the time of recording the radiation image thereon. Thereafter, in the main reading mode, a light beam of a higher level is applied to the stimulable phosphor sheet to read the recorded radiation image under the optimum reading conditions, thereby generating a final image signal.
Other radiation image recording and reproducing systems, which may or may not have the preliminary and main reading modes of operation, analyze an obtained image signal (which may include an image signal produced in the preliminary reading mode) to determine optimum image processing conditions with which the image signal is to be processed. Such a process of determining optimum image processing conditions based on image signals is employed in not only radiation image recording and reproducing systems which utilize stimulable phosphor sheets, but also radiation image recording and reproducing systems in which image signals are derived from radiation images recorded on X-ray films or the like.
The arithmetic operations or processes (hereinafter referred to as "EDR (exposed data recognition) sequence") which determine reading conditions and/or image processing conditions based on image signals are governed by an algorithm which was established by an statistic analysis of a number of radiation images. If the radiation image of an object accidentally contains an image of a large thing, e.g., a protector of lead for protecting the object from exposure to the radiation, or if the radiation image of an object is to be recorded in a very special way, then the EDR sequence according to the statistically established algorithm may not be effectively carried out. If the EDR sequence is not effectively carried out, then the recorded radiation image is not read properly and/or the image signal is not processed properly. Any visible image which is reproduced on the basis of the improperly read radiation image or the improperly processed image signal tends to have a density or contrast problem. If the reproduced image is too poor to be corrected, then the radiation image has to be canceled and a new radiation image has to be recorded again, resulting in a waste of time. When the object is a human body, the double exposure to the radiation is not preferable since the total radiation dose received by the human body is doubled. The above problem rises also when the image reading apparatus in the system fails for some reason or when the algorithm of the EDR sequence is not suited to the conditions in which the radiation image is recorded.
Smooth and efficient operation of the radiation image recording and reproducing system requires the system to be backed up by a well established maintenance procedure. When a fault occurs in the radiation image recording and reproducing system, a serviceman inspects the system fault and repairs the defective part on site if possible. If the defective device cannot be repaired on site, then it is replaced with a new device by the serviceman.
If the fault in the system cannot be located by the serviceman in the inspection procedure, then it is not possible for the serviceman to identify the defective part to be repaired or replaced on site. When this happens, the radiation image recording and reproducing system will not be available for service over a long period of time. Therefore, it is desirable to find any faulty part quickly if a system fault occurs.